1. Field of the Invention
The present invention relates to an image forming apparatus using an electrophotographic system, such as a copying machine, a printer, or an integrated machine of them, and particularly to an image forming apparatus constructed by plural modules made of independent structures in which the whole of the apparatus is very effectively divided into parts.
2. Description of the Related Art
In recent years, in a color copying machine or printer, except for a personal type in which importance is given to miniaturization, the size and weight of the whole apparatus tends to become large by the increase of basic structural parts accompanying color image formation and the increase of parts accompanying diversification of functions.
In general, such a copying machine or printer is often constructed such that an image forming portion for forming a toner image corresponding to image information, transferring it to a recording sheet, and then fixing it, a sheet supply portion for accommodating the recording sheet and transporting it to the image forming portion, and a sheet discharge portion for discharging the recording sheet after being fixed in the image forming portion to the outside are housed in one casing and are unified. Further, in the case of the copying machine, a document reading portion f or reading an image of a document is housed in the casing and a unified structure is made.
However, in the image forming apparatus, such as the copying machine or printer, in which the image forming portion, the sheet supply portion, and the discharge portion, and further, the document reading portion are housed in one casing and are unified like this, there are technical problems as described below.
First, there is a problem that since the image forming apparatus is made of one large casing, its packaging becomes large and the weight becomes heavy so that handling is difficult. Further, if a narrow place, such as an elevator or an entrance of a room, exists when the apparatus is transported for delivery or is moved to change the installation place, to pass through the place is difficult, and according to circumstances, it is impossible to transport or move it. Thus, there is a problem that the operations of transportation and movement are often inconvenient.
Besides, since all the structural parts generating operation sounds, such as driving parts or sheet conveying passages, are housed in one casing, the respective operation sounds are resonated to be amplified or become apt to leak out of the apparatus. Thus, there is a problem that a large noise is made at the time of image formation.
Besides, since all of the respective structural parts are housed in one casing, the conveying passage of the recording sheet often comes to have a complicated or abruptly bent structure such as an S-shaped or U-shaped structure. Thus, there is a problem that paper clogging or conveying sound becomes apt to be made, or it is difficult to remove the clogged paper. Since other structural parts are also provided in a state where they are close to each other, there is a problem that maintenance operations or exchange operations are hard to perform.
Moreover, although the number of recording sheets used becomes large as the speed of an image forming process is increased, it is difficult to enlarge the sheet supply portion already existing in the casing such that a large amount of recording sheets can be accommodated, and in the case where a large capacity tray or the like is added through later attachment to the apparatus body to meet the request, the apparatus installation space is increased. Thus, there is a problem that a suitable measure can not be made eventually.
Besides, since the mutual parts are provided in a state where they are close to each other in the casing, there is a possibility that an electromagnetic wave emitted from an electronic equipment such as a control circuit substrate adversely influences other parts, and further, there is a fear that lowering in picture quality is induced. Besides, there is also a fear that the electromagnetic wave induces an erroneous operation or the like of another electronic equipment existing at the periphery of the apparatus.
Incidentally, also in the prior art, there is proposed a copying system provided with a scanner module including a unit to read an image of a document, a printer module including a unit to form image data as an eternal visual image on a recording medium and output it, and a system control module including a unit to control the scanner module and the printer module such that they are operated in synchronization (Japanese Patent Unexamined Publication No. Hei. 6-276334).
However, in this copying system, in the case where the three basic modules and a table (or a selection multi-stage paper feeding device) are combined, since it is designed such that those are preferably vertically combined (see a disclosure in paragraph 0024, FIG. 20, etc.), there is a problem that a size increase in height direction can not be avoided. Besides, since the print module, including a one-stage paper feeding device, is provided with a function up to a step of discharging a recording sheet after fixing to the outside of the apparatus (see FIG. 8, etc.), it is apt to become large. Besides, since many structural parts are provided in one casing in a close state, there is a problem that maintenance and exchange operations of each structural part are hard to perform. Further, in the print module, since a driving system or a sheet conveying passage which becomes a generating source of operation sound is also housed in one casing, there is also a problem of noise as described before.